1. Field of the Invention
The present invention relates to a packet data communication system, and more particularly to a method for transmitting and receiving packetized data having a multi-protocol header.
2. Description of the Related Art
As a protocol for transmitting data through the Internet, transmission control protocol (TCP) is described in Request For Comments (RFC) 793 issued by the Internet Engineering Task Force (IETF). TCP is used for transmitting data in packet format between nodes of the Internet. In the network layer hierarchy, TCP functions as the protocol of the transport layer. Below the transport layer is the network layer, which uses internet protocol (IP).TCP and IP are collectively referred to as TCP/IP.
In typical data transmission technologies based on TCP/IP, packetized data contains at least one header used for controlling a network protocol function. Because the header consumes part of the available bandwidth for a communication channel, research on various technologies for compressing the header to optimally use the bandwidth is ongoing.
The need for TCP/IP header compression is increased in a wireless communication system designed to transmit voice and/or data using a radio frequency (RF), which is typically noisier and has greater bandwidth limitations than wired communication systems.
Van Jacobson has proposed a method for compressing a TCP/IP header. The proposed method removes redundant static information from a TCP/IP packet and contains, in the packet, difference values required to determine changing information. One of two nodes (hereinafter, referred to as a transmitting node) periodically transmits packets containing uncompressed headers (hereinafter, referred to as full packets) to another node (hereinafter, referred to as a receiving node). The transmitting node removes the static information from the full packets, and leaves only the difference values of the changing information in headers of the packets so that the transmitting node can transmit, to the receiving node, packets having compressed headers (hereinafter, referred to as compressed packets). Upon receiving the compressed packets, the receiving node refers to information in the headers and decompresses the headers of the compressed packets.
However, if one of a series of packets is damaged or lost because an operating state of the communication channel is bad and the network is in a congested state, the receiving node will be unable to decompress the headers of the compressed packets transmitted by the transmitting node. Further, the receiving node will not send an acknowledgement associated with the damaged or lost compressed packet, and the receiving node will request the transmitting node to retransmit a corresponding compressed packet after receiving a full packet corresponding to the damaged or lost compressed packet. As a result, the receiving node is required to store all of the compressed packets received after a packet loss until a full packet corresponding to the lost packet is received.
Thus, simple technologies for compressing and transmitting a header of a TCP/IP packet can address some problems associated with repeatedly transmitting static information, but can cause the above-described serious problems in radio frequency (RF) environments. In particular, errors may frequently occur in RF environments. If a packet transmission error occurs, a data reception operation must be stopped until a damaged or lost packet is retransmitted. As a result, simple compression schemes can cause the efficiency of transmission to be severely degraded in noisy environments.